Phytoplankton

Number of species

Number of species over time

Benthos

Number of individuals

Number of individuals over time

Number of species

Number of species over time

Diversity

Diversity over time

Relative abundance - taxon

Fishes

Number of individuals

Number of individuals over time

Number of species

Number of species over time

Diversity

Diversity over time

Relative abundance

Species composition over time

Fishes - seine net only

Number of individuals

Number of individuals over time

Number of species

Number of species over time

Diversity

Diversity over time

Relative abundance

Species composition over time

Top 10 most abundant species

Flounder

Flounder spends most of its life in coastal waters but move into deeper, warmer waters in winter this can be up to 300 km offshore. The spawning population remains in the open sea to breed and spawning usually takes place from March to June migrate into the open sea. Males and females reach sexual maturity at different times; males mature at around 11cm length and females at around 17cm. Juveniles immigrate into estuaries in early May and settle on the seafloor where they live until they are ready to migrate and spawn, morphing into the flatfish form.

Average number of individuals

Average length

Dace

Freshwater/brackish species. Spawn March to May. Larvae and juveniles commonly found along shallow shoreline areas, adults are found in faster flowing waters. Maximum larval length 40 mm. Average adult length 15 cm.

Average number of individuals

Average length

Roach

Freshwater/brackish species. Found across a variety of habitats but generally overwinters in deep waters. Spawns May to June. Larvae and juveniles found in shallower, shoreline areas. Maximum larval length 40 mm. Average adult length 25 cm.

Average number of individuals

Average length

Sand goby

Marine/brackish species found in coastal habitats with a sandy or muddy bottom into which they can bury. Juveniles found in lower estuarine habitats. Larvae are pelagic until 17 mm length, when they start living on the bottom. Maximum larval length 12 mm. Sexually mature from 3 cm length. Maximum adult length 11 cm.

Average number of individuals

Average length

Sea bass

Marine/freshwater/brackish species that is commercially important and popular with recreational fishers. Spawning takes place from March to June in shallow coastal waters and estuaries. Juveniles usually stay in brackish nursery waters until their second summer (>210 mm in length). Adult fish migrate to deep waters during the colder months. They are a long-lived species that can live up to 20 years in age. In UK waters they do not become sexually mature until around six to eight years and are therefore vulnerable to exploitation without strict implementation of minimum catch sizes and protected nursery areas. Maximum larval length 40 mm. Sexually mature from 23 cm length. Average length of adult 60 cm (maximum 100 cm). The Thames Estuary is now the largest sea bass nursery in the south of England.

Average number of individuals

Average length

Common goby

Marine/freshwater/brackish species, usually found on sandy or muddy substrate into which they can bury. Spawning occurs between February and September at sea or in brackish water. Maximum larval length 11-12 mm. Sexually mature from 3 cm length. Maximum adult length 9 cm.

Average number of individuals

Average length

Sprat

Marine/brackish species. Commercially important, sprat is commonly found in estuaries. Spawning takes place in spring and early summer out to sea and the eggs and larvae drift inshore over the summer months. Sprat are commonly found in mixed shoals with juvenile herring. To distinguish between the species look for the position of the dorsal and pelvic fins. In sprat, the front of the dorsal fin is behind the base of the pelvic fin, but in herring the front of the dorsal fin is in front of the pelvic fin. Maximum larval length 40 mm. Sexually mature at 13-15 cm. Average adult length 12 cm.

Average number of individuals

Average length

Smelt

Marine/freshwater/brackish species found in western Europe. They migrate to freshwater to spawn from March to April. Entirely freshwater populations are known to occur. Found in estuaries and coastal areas. A valuable indicator species due to sensitivity to pollution, UK populations suffered severe declines since the 19th century. Signs of recovery have been observed but they are still threatened by poor water quality and barriers to migration such as weirs and dams. Maximum larval length 40 mm. Sexually mature from 8 cm length. Average length of adult 16.5 cm.

Average number of individuals

Average length

Dover sole

Marine/brackish species. Juveniles form nurseries in coastal and estuarine habitats for first three years of life. Adults swim to deeper waters during winter months. Hatch as symmetrical fish before metamorphosing to flat fish with both eyes usually on the right-hand side at about 10 mm length. Maximum larval length 40 mm. Sexually mature from 25 cm length. Average length of adult around 30-40 cm (maximum 70 cm).

Average number of individuals

Average length

Whiting

Marine/brackish species, with juveniles found in shallower coastal and estuarine habitats and are often found with jellyfish. Maximum larval length 40 mm. Average adult length 30-40 cm.

Average number of individuals

Average length

European eel

Marine/freshwater/brackish species. Listed as Critically Endangered by the International Union for the Conservation of Nature (IUCN). Catadromous species, they can spend most of their lifecycle in freshwater but migrate in from the sea as glass eel and elver before returning back to the sea to spawn. Elver are most commonly found from April to October throughout the length of estuaries. Average length adult 35 cm (male) to 60 cm (female).

Average number of individuals

Average length